Tests determining various measures of error, such as bit error rate (BER) and block error rate (BLER) (also referred to as packet error rate (PER)), are used to evaluate performance of signal receivers, such as radio frequency (RF) receivers in wireless telecommunication systems. BER and BLER tests, in particular, are commonly required by conformance tests for wireless communication standards, such as Wideband Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE), and the like. Likewise, BER and BLER tests may be required for wireless devices or systems configured in accordance with various high-speed interface standards. For example, the Common Public Radio Interface (CPRI) standard defines an internal digital interface between Radio Equipment (RE) and the corresponding Radio Equipment Controller (REC). Similarly, the DigRF standard defines an internal digital interface between Radio Frequency IC (RFIC) and the corresponding Baseband IC (BBIC).
When testing devices or systems with respect to high-speed interface standards, the device under test (DUT), e.g., the RE in the CPRI standard and the RFIC in the DigRF standard, has a down-converter and an analog-to-digital converter (ADC). Accordingly, the DUT is able to generate digital in-phase and quadrature (IQ) baseband data from an RF input signal after some front-end processing, such as filtering and automatic gain control (AGC).
Because of the large amount of IQ baseband data output by the DUT, conventional BER and BLER testing of an internal high-speed interface cannot be performed adequately using standard test equipment, such as a typical signal analyzer. Rather, the BER and BLER testing requires use of dedicated test hardware designed to process large amounts of data at a very high speed. For example, when the DUT is an RE according to the CPRI standard or an RFIC according to the DigRF standard, the DUT is connected to a dedicated test apparatus that simulates the REC or the BBIC, respectively. The dedicated test apparatus has the capability of demodulating and decoding signals output by the DUT, and thus is able to detect error bits or frame errors. Additional software may accumulate results to calculate the BER and BLER of the DUT. However, manufacturers of the DUTs (e.g., the REs and RFICs) typically do not have dedicated test apparatuses capable of calculating the BER and BLER, particularly when they do not also manufacture the RECs or BBICs.
An alternative conventional approach is to send the IQ baseband data from the DUT to a computer, such as a personal computer (PC) or a laptop computer. The computer executes a software program, such as SystemVue or Advanced Design System (ADS) available from Agilent Technologies, or MATLAB available from MathWorks, which processes the IQ baseband data by demodulating and decoding the IQ baseband data and performing the BER and BLER calculation. However, such calculation of the BER and BLER is very time consuming in order to obtain reliable results by processing a large amounts of data, particularly under low bit error rate conditions.
As a result, the manufacturers do not have an efficient or inexpensive way in which to test BER and BLER performance of the high-speed interfaces, for example, of REs and RFICs. The testing issue becomes more difficult for higher speed wireless communications, such as next generation wireless broadband standard, LTE (4G).